Referring to South Sudanese model Nykhor Paul, who recently hit out at make-up artists on Instagram for not being equipped with the right products to compliment her skin tone, Iman says exactly the same situation prompted her to set up her own - now globally successful - make-up line, Iman Cosmetics.

"In 1975, a makeup artist asked me if I brought my own foundation," she recalls. "But now, every line from François Nars's to Iman to Bobbi Brown has a lot of skin tones.

"So, good for her [Nykho] — the laziness and audacity of those makeup artists! It’s not like you didn’t know this model was going to be there. Make-up artists already know. And why shouldn’t you have the foundation — that’s your job. It’s like hiring a painter to come paint your house and he’s forgotten your paint and has to ask for it! You should get fired, you should be fired!"

The Somali-born model and actress also revealed that her career in the spotlight has not always been easy.

"I suffer from low self-esteem," she says. "I had horrible self-esteem growing up. You really have to save yourself because the critic within you will eat you up. It’s not the outside world, it’s your interior life, that critic within you that you have to silence.

"Find something to like about yourself and hold on to that. It’s a constant battle whether you are 16 or 50. As you age, you do really find that quietness inside and that being-comfortable-in-your-skin feeling."

Iman has been married to singer David Bowie since 1992 and has two children.

Having just turned 60, she adheres to a series of therapeutic rituals to maintain a sense of wellbeing.

"I like to get up around 5:30 or six — that’s my favourite time of day," she says. "My family is still asleep and the office is still closed, so I can start my day slowly. I first have a glass of warm water with lemon. And then I lie down and keep my mind clear for about 20 to 30 minutes. I get up and have a cup of coffee and slowly ease into it.

"My ritual is cooking. I find it therapeutic," she adds. "It comes naturally to me.

"...I started cooking when I began dating my husband. During my modeling years, I didn’t cook. We got up at 10 or 11pm and then went out, eating at 4 or 6 am before going to bed. Life is too short not to have pasta, steak, and butter. I like moderation, but I like the idea of having vegetables a few times a week. I don’t love eating meat. I really only like chicken and fish."

As for fitness, she says, "I go and do Pilates three to four times a week. It is very challenging, but I still find it boring. As I age, cardio is the most important thing. Not feeling out of breath is the thing that I miss most."

Iman in the 1987 film No Way Out

On the topic of ageing, Iman says, "I feel pretty good. I feel really healthy, loved, blessed, and I’ve never been more comfortable being inside myself. I’ve been forced to sit still. I tell my younger friends, 'Don’t be afraid of change. That is when you really see what your destiny is'.

"...I don’t read the comments, really, but someone once commented, 'Oh my God, she looks so good for 70,'" she notes. "And I said, 'Bitch, don’t rush me! I’m 60, not 70.'"